The present invention relates to apparatus and methods for filtering or removing matter from within the vascular system. More particularly, the present invention provides a low profile self-expanding vascular device useful in the ascending aorta for capturing emboli generated during vascular procedures.
Percutaneous interventional procedures to treat occlusive vascular disease, such as angioplasty, atherectomy and stenting, often dislodge material from the vessel walls. This dislodged material, known as emboli, enters the bloodstream, and may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. The resulting ischemia poses a serious threat to the health or life of a patient if the blockage occurs in critical tissue, such as the heart, lungs, or brain.
The deployment of cannulas, cross clamps or occlusion balloons during bypass surgery, or stents and stent-grafts to treat vascular disease also involves the introduction of foreign objects into the bloodstream and may result in the formation of clots or release of emboli. Such particulate matter, if released into the bloodstream, also may cause infarction or stroke.
Numerous previously known methods and apparatus have been proposed to reduce the risk of embolism. U.S. Pat. No. 5,833,644 to Zadno-Azizi et al., for example, describes the use of balloon-tipped catheter to temporarily occlude flow through a vessel from which a stenosis is to be removed. Stenotic material removed during a treatment procedure is evacuated from the vessel before the flow of blood is restored. A drawback of such previously known systems, however, is that occlusion of antegrade flow through the vessel may result in damage to the tissue normally fed by the blocked vessel.
U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli filter system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and any interventional devices, such as angioplasty balloons or stent delivery systems, are advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter. Similar filter systems are described in U.S. Pat. No. 4,723,549 to Wholey et al., and U.S. Pat. No. 5,827,324 to Cassell et al.
One disadvantage of radially expandable filter systems such as described in the foregoing patents is the relative complexity of the devices, which typically comprise numerous parts. Connecting more than a minimal number of such parts to a guide wire generally reduces the ability of the guide wire to negotiate tortuous anatomy and increases the profile of the device in its delivery configuration. Moreover, such filter devices are generally incapable of preventing material from escaping from the filter during the process of collapsing the filter for removal.
International Publication No. WO 98/39053 describes a filter system comprising an elongated member, a radially expandable hoop and a cone-shaped basket. The hoop is affixed to the elongated member, and the cone-shaped basket is attached to the hoop and the elongated member so that the hoop forms the mouth of the basket. The filter system includes a specially configured delivery catheter that retains the mouth of the basket in a radially retracted position during delivery.
While the filter system described in the foregoing International Publication reduces the number of components used to deploy the cone-shaped basket, compared to the radial strut-type filter elements described hereinabove, it too has drawbacks. Chief among these, it is expected that it will be difficult to reduce the diameter of the radially expandable hoop to its retracted position. In particular, as the hoop is contracted through smaller radii of curvature, the stiffness of the hoop is expected to increase dramatically. This increased stiffness prevents the hoop from being contracted more tightly and is expected to result in a large delivery profile.
In view of the foregoing disadvantages of previously known apparatus and methods, it would be desirable to provide a vascular device, e.g., for use as a vascular filter in the ascending aorta, that, overcomes such disadvantages, and employs few components.
It also would be desirable to provide a vascular device that is capable of being contracted to a small delivery profile.
It further would be desirable to provide a vascular device that is capable of being advanced into position from the downstream direction of blood flow.
It still further would be desirable to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
In view of the foregoing, it is an object of the present invention to provide a vascular device, e.g., for use as a vascular filter in the ascending aorta, that overcomes disadvantages associated with previous vascular filters and thrombectomy/embolectomy devices, and employs few components.
It is another object of the present invention to provide a vascular device that is capable of being contracted to a small delivery profile.
It is yet another object of the present invention to provide a vascular device that is capable of being advanced into position from the downstream direction of blood flow.
It is a further object of this invention to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
These and other objects of the present invention are accomplished by providing a vascular device suitable for use as a vascular filter in the ascending aorta that comprises a blood permeable sac affixed at its perimeter to a support hoop having an articulation region. The support hoop is attached in a distal region of an elongated member, such as a guide wire, and supports a distally-oriented mouth of the sac when the device is deployed in a vessel. In accordance with the principles of the present invention, the support hoop includes a reduced-thickness articulation region that enables the support hoop to be contracted to very small radii of curvature without the problems of increased stiffness and kinking of previously known devices. The vascular device may therefore be used with delivery sheaths having diameters as small as 0.060xe2x80x3.
The support hoop preferably also has a curved profile that prevents the articulation region, when folded, from damaging the wall of the vessel. The curved profile also permits the device to effectively contact the walls of the vessel and reduce emboli or thrombus removed from the vessel wall from bypassing the sac. The articulation region, when combined with a support hoop having a curved profile, causes the sides of the support hoop to fold inwards towards one-another when the vascular device is collapsed into a sheath for removal. This, in turn, closes the mouth of the sac and reduces the potential for emboli or thrombus to be released from the vascular device during removal.
Methods of using the vascular device of the present invention are also provided, particularly in the context of a vascular filter placed in the ascending aorta.